Ella worships Hadley. She wants to do everything that big sister does and be involved in everything big sister does. Hadley's bike has pegs on the back wheel, and Hadley has just now started to let Ella ride on them.
Ella thinks it is so wonderful that she can ride a bike with Hadley. It's a dream come true for her. I, of course, think it's ridiculously adorable. :)